Exploring Deep Nepheloid Layers in Mexican and U.S. Gulf of Mexico Waters, Summers of 2015-2017

Bottom nepheloid layers of variable strength were observed in summers of 2015-2017 in the central and southwestern deep waters of the Gulf of Mexico west of the Yucatan peninsula. The most intense benthic nepheloid layers occurred in 2015 on the abyssal plain and lower slopes in the west, in contrast to 2016 and 2017 when the benthic nepheloid layers were weaker and less abundant. Bottom maps and vertical sections of particulate matter (PM) concentration throughout the water column (converted from beam attenuation measurements) show evidence of sediment resuspension, most probably linked with eddies in the deep Gulf of Mexico and eddy-topography interactions. The data were collected on Mexico’s B/O Justo Sierra vessel during three cruises in the deep-water region of the Gulf of Mexico. We will compare the areas of strong nepheloid layers with new data on sediment accumulation rates and with circulation patterns in the deep Gulf of Mexico recently published by other researchers using four years of measurements from floats and moorings at 1500m and 2500m. Additional PM measurements were made along cross-slope transects around the entire Gulf of Mexico, including across the Yucatan and Florida straits during the U.S. GOMEX program on the R/V Ron Brown in 2017. PM concentrations were not elevated in either of the straits at that time.